Answer and Explanation:
A. Hello. You did not enter answer options. However, we can state that mutation, natural selection and genetic drift will be the microevolution mechanisms that will affect the gene pool of these humans. This is because the new environment and the small number of living beings, will make this population completely susceptible to all these evolutionary factors, which will affect, in different ways, the gene frequencies in a population.
B. As the amount of living beings and human beings has become very small, the world will have a low genetic diversity. This will make it difficult for these humans to adapt to the new environment and will make them more susceptible to possible diseases that will arise in this new environment. This will make these humans more fragile and make it harder for them to multiply.
C. The evolution mechanism is the Gene Flow. Gene Flow refers to the exchange of genetic information between individuals in a population, through the donation of gametes that occur in reproductive processes. In this case, we can consider that the individual with green eyes, upon arriving in the community with individuals without green eyes, began to reproduce descendants, who, upon receiving the gametes responsible for green eyes, began to populate this community with this characteristic.